This invention relates to structures and has a particularly useful application in buildings such as airport visual control rooms where an angle of at least 180.degree. of uninterrupted vision is desirable. To minimize visual distortion effects in airport visual control rooms, flat glass panels are employed which are inclined downward at an angle of 15.degree. to the vertical, and the control rooms may be of pentagonal, hexagonal, octagonal or other polygonal form. The glass panels are mounted in similarly inclined mullions which conventionally support also the roof of the control room. The mullions are therefore necessarily of strong construction and interrupt the field of view to a small but not negligible extent.